/*
 * A state model for the extjs TreePanel. Use the init method
 * to initialize the object and don't forget to attach the
 * the expand and collaps event handlers on your TreePanel.
 *
 * 10. July 2007
 * gnaegi@frentix.com
 */
function TreePanelState(mytree) {
	this.mytree = mytree;
}

/*
 * The init method must be called after object creation
 * to initialize the cookie provider
 */
TreePanelState.prototype.init = function() {
	this.cp = new Ext.state.CookieProvider();
	this.state = this.cp.get('TreePanelState_' + this.mytree.id, new Array() );
}

/*
 * Internal helper to save state in cookie.
 */
TreePanelState.prototype.saveState = function(newState) {
	this.state = newState;
	this.cp.set("TreePanelState_" + this.mytree.id, this.state);
}

/*
 * Method should be called when expanding a node. 
 * The method removes all contained pathes from the
 * state model, they are implicitly opened by this
 * new path.
 */
TreePanelState.prototype.onExpand = function(node) {
  	var currentPath = node.getPath();
  	var newState = new Array();
	for (var i = 0; i < this.state.length; ++i) {
		var path = this.state[i];
		if (currentPath.indexOf(path) == -1) {
			// this path does not already exist
			newState.push(path);			
		}
		// ignore contained path, implicitly opened by new path
	}
	// now ad the new path
	newState.push(currentPath);
	this.saveState(newState);
}

/*
 * Method should be called when collapsing a node. 
 * The method removes all contained pathes from the
 * state model.
 */
TreePanelState.prototype.onCollapse = function(node){
	var closedPath = closedPath = node.getPath();
    var newState = new Array();
	for (var i = 0; i < this.state.length; ++i) {
		var path = this.state[i];
		if (path.indexOf(closedPath) == -1) {
			// this path is not a subpath of the closed path
			newState.push(path);			
		}
		// ignore pathes that are contained in the closed path
	}
	if (newState.length == 0) {
		var parentNode = node.parentNode;
		newState.push((parentNode == null ? this.mytree.pathSeparator : parentNode.getPath()));
	}
	this.saveState(newState);
}

/*
 * Restore the last state from the cookies or use 
 * the default path if no state has been found.
 */
TreePanelState.prototype.restoreState = function(defaultPath) {	

	if (this.state.length == 0) {
		var newState = new Array(defaultPath);
		this.saveState(newState);		
		this.mytree.expandPath(defaultPath);
		return;
	}

    var stateToRestore=this.state;

	for (var i = 0; i < stateToRestore.length; ++i) {
		// activate all path strings from the state
		try {
			var path = this.state[i];
		    this.mytree.expandPath(path);  		
		} catch(e) {
			// ignore invalid path, seems to be removed in the datamodel
			// add debugging here if your tree does not expand as expected
		}
	}	
}